1. Field of the Invention
The present invention relates to signal output devices and, more particularly, to signal transmitters and driving methods thereof.
2. Description of the Prior Art
FIG. 1 is the block diagram of a prior art signal output device 10. The signal output device 10 comprises a signal transmitter 12 and a display device 14. The signal transmitter 12 comprises a signal processing circuit 16, an output circuit 18, and a connection port 20. The data processing circuit 16 decodes the signal DATA inputted to the signal processing circuit 16 and outputs an image signal DATA′. The output circuit 18 transforms the digital signal DATA′ into an analog signal DATA″, and the signal DATA″ is transmitted to the display device 14 through the connection port 20 and a connecting line 22. The display device 14 then displays the image corresponding to the signal DATA″.
If the signal transmitter 12 is not connected to the display device 14, the signal transmitter 12 is not able to drive the display device 14 when the signal transmitter is powered on because the connection between the signal transmitter 12 and the display device 14 is broken. However, the signal processing circuit 16 and the output circuit 18 begin to dissipate power when they are powered on, and this results in an unnecessary waste of power in the signal transmitter 12. If such a signal transmitter is used in portable electronic devices, such as a notebook, it will definitely shorten the time the battery is able to supply power.